You will have to prepare the old construction component before the actual removal. If furniture, tiles or laminate are in the closer surrounding, they should be covered with either a sheet or foil.
Window sills are sometimes plastered into the masonry. The plaster can fall of while removing an aluminium, uPVC or natural component and can dirty furniture, tiles and laminate. Especially when working with a crowbar or chisel, take care, as flying fragments may damage the frame. This is why it is recommended to cover the frame as well.
You should re-measure the dimensions of the old window sill and compare it with the new one before removing it. This will ensure that the installation process can be performed smoothly (Fig. 1).